Carotenoids, i.e. compounds such as bixin, lutein, beta-carotene, zeaxanthin, beta-apo 8'-carotemal, canthaxanthin, capsanthin, and esters of hydroxylated carotenoids have become increasingly important as food colorants in recent years as a result of findings that certain azo- and triphenyl methane food colors are toxic. The banning of F,D&C Red No. 2, F,D&C Red No. 4 and F,D&C Violet No. 1, and recent review of the toxicity of F,D&C Red No. 40 and F,D&C Yellow No. 5 are examples that affect the development and increased use of natural colorants in foods.
Carotenoids are naturally present in edible leaves, flowers and fruits, and are considered to be non-toxic for human consumption. Carotenoids are yellow to red pigments, and their potential use in foods has been limited as a result of their poor solubility in water and vegetable oil, as well as their non-availability in uniform and concentrated form. Annatto, saffron, and paprika are few natural carotenoid containing materials traditionally used for coloring foods.
In plants the hydroxylated carotenoids (xanthophylls) occur acylated with fatty acids and the xanthophyll-fatty acid esters are highly soluble in oil as compared to their parent xanthophylls. Thus xanthophyll-fatty acid esters could be used directly for coloring fat-based foods and the technology for their use in water-based foods is available.
Marigold flower petals, Tagetes erecta contain one of the highest known concentrations of lutein in nature (Scott, M.I., Ascarelli, I. and Olson, G. 1968. Poultry Science 47: 863). Marigold which can be cultivated easily, is commercially grown in Central America and the dried flowers are used as a pigment source for poultry. Lutein which accounts for over 60% of the total xanthophylls in marigold flowers occurs acylated with palmitic and myristic acids (Philip, T. and Berry, J.W. 1975. J. Food Science 40: 1089). Lutein is universally present in leaves and is reported to be present in several edible fruits (Philip, T. and Berry, J.W. 1976. J. Food Science 41: 23). Lutein is the major colorant present in egg yolks and thus lutein is consumed by humans directly through eggs or indirectly through food products containing eggs.
The high concentration of lutein in marigold flower petals, the high solubility of lutein-fatty acid esters in vegetable oil, and the known nontoxicity of lutein make it an attractive colorant for human foods.